﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using System.Xml;
using System.Xml.Serialization;
using System.IO;

namespace Celeriq.Utilities
{
	public static class Extensions
	{
		internal static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge)
		{
			// build parameter map (from parameters of second to parameters of first)
			var map = first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }).ToDictionary(p => p.s, p => p.f);

			// replace parameters in the second lambda expression with parameters from the first
			var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);

			// apply composition of lambda expression bodies to parameters from the first expression 
			return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);
		}

		/// <summary>
		/// Concatenate Lambdas using the AND operation
		/// </summary>
		public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
		{
			return first.Compose(second, Expression.And);
		}

		/// <summary>
		/// Concatenate Lambdas using the OR operation
		/// </summary>
		public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
		{
			return first.Compose(second, Expression.Or);
		}

		/// <summary>
		/// Can compare 2 strings with case insensitivity
		/// </summary>
		public static bool Contains(this string source, string toCheck, StringComparison comp)
		{
			return source.IndexOf(toCheck, comp) >= 0;
		}

	}
}
